In a communication system a communication network is provided, which can link together at least two communication terminals so that the terminals can send information to each other in a call or other communication event. Information may include speech, text, images or video.
Digital communication systems are based on the transmission of digital signals. Analogue signals such as light waves are input into a recording device such as a camera and recorded by an image sensor such as a charged coupled device (CCD) in the camera. Data recorded by the image sensor is then converted into digital data by an analogue to digital converter. The digital signal is then encoded and placed into data packets for transmission over a communication network.
Each data packet includes a header portion and a payload portion. The header portion of the data packet contains data for transmitting and processing the data packet. This information may include an identification number and source address that uniquely identifies the packet, a header checksum used to detect processing errors and the destination address. The payload portion of the data packet includes the encoded video data intended for transmission.
The transmission of high quality images, such as those with a high resolution, may require large amounts of data to be encoded and transmitted via the communication network, particularly during real time communication events such as video calls and video streaming. This consumes a large amount of CPU (Central Processing Unit) resource of the transmitting terminal and of the receiving terminal which in turn increases the power consumption of the terminals. The transmission of large amounts of data will also consume the bandwidth of network, thereby increasing introducing packet loss and delay.
The transmission of high quality images may require complex compression methods to encode the data, such encoding methods may again consume a large amount of CPU resource.
A further problem with transmitting high quality images is that this can overload the CPU resources of the terminals thereby adversely affecting the operation of the terminal to display the image and perform other processing functions.
The burden on the CPU resources of the terminals may be alleviated by sending data at a low resolution. However this can also adversely affect the quality of the displayed image. This is particularly noticeable to a user when the display screen on which the image is displayed is large and has a high resolution.
It is therefore an aim of the present invention to overcome the above identified problems by efficiently encoding and transmitting information over the network without affecting the perceived quality of the image displayed at the receiving terminal.
It is a further aim of the invention to improve the perceived quality of the image data when it is displayed at a receiving terminal.